The other day, I went to Hobby Lobby hoping to use a coupon on an F50-6 motor. It appears I have no will power even though SU motors are more expensive than reloads. They had no F50s (i.e. they sold the one they keep on the racks) so I bought an F26-6FJ, which is also a recommended motor for the Ventris. When I got home, I began thinking about the previous two flights. The F32 flight went well but there was some weather cocking. The F52 flight was arrow straight, but a -6 delay was a tad long. I had concerns about an F26 so I went back to RockSim. I now know the F26-6 is not optimal for my kit and have serious doubts about any Ventris. Admittedly, mine is about 2.5 oz heavier than the projected weight (18 vs.15.6 oz.). I added a hefty swivel to the 'chute, used a quicklink, added rail buttons, etc. The loaded weight of 21.5 oz is perilously close to the unsafe range based on the thrust-weight chart on ROL Info-Central. With a 5' rail and a -4 delay, you could still probably use the F26 but I'll save my -6 for another rocket on another day.
I decided an F35 in the 24/60 case would be a better choice. I even have an adapter that I built for the F32 flight. [insert sound of a vinyl record scratching to a halt] Luckily, I test fit the motor - the retainer cap wouldn't screw on! Evidently, the wider thrust ring/closure was just large enough that it wouldn't fit. Before I show my solution, I also became concerned about the AeroTech HP casings which have an even wider thrust ring (but obviously no adapter is required). I tested a 29/180 case and the retainer will screw on. However, it doesn't have many threads holding it in place. Now that I installed one of these retainers on my NCR Archer, I am contemplating using a washer retainer as insurance.